1. Brief Description of the Invention
The present invention relates to a method for loading tool steel and high speed steel powder into a deformable mold for compacting, with the powder during transport to the mold being under dynamic, uniform vacuum.
2. Brief Description of the Prior Art
Incident to the powder-metallurgy production of tool steel and high speed steel articles, prealloyed particles of the composition from which the article is to be made are loaded into a deformable container. This deformable container is then sealed and the prealloyed particles therein are consolidated by hot isostatic pressing within a gas-pressure vessel. To achieve the desired product quality, particularly from the standpoint of uniformity of microstructure and the absence of deleterious impurities, such as oxides, it is important that the powder be free of these impurities at the time of compacting. This is typically achieved by outgassing the deformable mold after the powder has been loaded therein and before sealing for consolidation as by hot isostatic pressing. As a result of the significant size and quantity of powder within the mold, it is difficult to achieve removal of impurities during outgassing uniformly with respect to the powder from top to bottom of the mold. Typically, the powder at the top of the mold, which is near the stem through which outgassing is accomplished, is at a much lower impurity level than the powder at the bottom of the mold. Consequently, after consolidation, the impurity level and thus the properties of the consolidated article may vary along the length thereof.